Glial cells

Glial cells within the peripheral nervous system produce myelin to encapsulate axons. Not all axons are surrounded by myelin. It acts to provide electrical insulation and so increase conduction speeds. Glial cells can be divided into:

• macroglia:
  • Schwann cells; the counterparts of oligodendrocytes within the CNS
  • derived from neuroectoderm embryonically
  • produced myelin sheath:
    • myelin is 70% lipid and 30% protein
    • produce a sheath of myelin that wraps multiple times concentrically around a neurone
    • only produces sheath for short distances, typically 1mm
    • intervals between Schwann cells are called nodes of Ranvier and are important in action potential conduction
• microglia:
  • macrophages and similar phagocytes
  • mobilised after injury in processes like Wallerian degeneration